III-V group nitride semiconductors have been variously applied to an optical device such as blue and green LEDs (Light Emitting Diodes), a high speed switching device, such as a MOSFET (Metal Semiconductor Field Effect Transistor) and an HEMT (Hetero junction Field Effect Transistors), and a light source of a lighting device or a display device. Particularly, a light emitting device using the group III nitride semiconductor has a direct transition-type bandgap corresponding to the range of visible rays to ultraviolet rays, and can perform high efficient light emission.
A nitride semiconductor is mainly used for the LED or an LD (laser diode), and studies have been continuously conducted to improve the manufacturing process or the light efficiency of the nitride semiconductor.